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X Rojas

Publications and source records attributed to X Rojas.

10 recordsLinked to original sources
PubMed2005

Towards single screening tests for brucellosis.

This paper describes an indirect enzyme-linked immunosorbent assay (I-ELISA) and a fluorescence polarisation assay (FPA), each capable of detecting antibody in several species of hosts to smooth and rough members of the genus Brucella. The I-ELISA uses a mixture of smooth lipopolysaccharide (SLPS) and rough lipopolysaccharide (RLPS) as the antigen, and a recombinant protein A/G conjugated with horseradish peroxidase as the detection reagent. When using individually determined cutoff values, the SLPS/RLPS combined-antigen I-ELISA detected antibody in slightly more animals exposed to SLPS or to RLPS than did I-ELISA procedures using each individual antigen separately. Similarly, the assay using combined antigens detected antibody in slightly fewer animals not exposed to Brucella sp. When a universal cutoff of 10% positivity was used (relative to strongly positive control sera of each species), the overall performance index (percentage sensitivity plus percentage specificity) value decreased by 1.0 (from 199.4 to 198.4). In the FPA, it was not possible to use a universal cutoff without significant loss of performance. The overall sensitivity value for the FPA using the combined FPA antigen was 1.0% lower than using the O-polysaccharide (OPS) from SLPS and 9.1% higher than using the core antigen (CORE) from RLPS. When the combined antigen was used, the FPA specificity was slightly higher (1.2%) than from only the OPS, and considerably higher (12.6%) than the CORE. Overall, both the I-ELISA and the FPA with combined antigens were suitable as screening tests for all species of Brucella in the animal species tested.

Animal Diseases↗
PubMed2004

Enzyme immunoassay for the diagnosis of brucellosis: chimeric Protein A-Protein G as a common enzyme labeled detection reagent for sera for different animal species.

A recombinant protein combining the immunoglobulin binding sites of Proteins A and G, conjugated with horseradish peroxidase was used as a universal detection reagent for the assessment of antibodies against Brucella spp. The reagent was applied in an indirect enzyme immunoassay for detection of antibodies to smooth lipopolysaccharide antigen in sera from Brucella spp. exposed and non-exposed cattle, sheep, goats and pigs and to antibodies to rough lipopolysaccharide in sheep, dogs and cattle. The results were similar to those obtained when murine monoclonal antibody-enzyme conjugates were used. An added advantage was that a universal cut-off for all tests using the proteins A and G detection reagent could be established, simplifying diagnostic interpretation of the data.

Animals↗
PubMed2004

Rough lipopolysaccharide of Brucella abortus RB51 as a common antigen for serological detection of B. ovis, B. canis, and B. abortus RB51 exposure using indirect enzyme immunoassay and fluorescence polarization assay.

Rough lipopolysaccharide (RLPS) antigens were prepared from cultures of Brucella abortus RB51, B. ovis, and B. canis. The preparations were standardized by weight and tested with sera from cattle immunized with B. abortus RB51, sheep infected with B. ovis, and dogs infected with B. canis. Populations of unexposed animals of each species were also tested. The tests used were the indirect enzyme immunoassay (IELISA) using RLPS and the fluorescence polarization assay (FPA) using RLPS core fractions, labeled with fluorescein isothiocyanate. The IELISA using B. abortus RB51 RLPS antigen resulted in sensitivity and specificity values of 94.8% and 97.3%, respectively, when testing bovine sera, 98.5% and 97.8% when testing ovine sera, and 95.8% and 100% when testing dog sera. The IELISA using B. ovis RLPS antigen gave sensitivity and specificity values of 80.5% and 91.7%, respectively with bovine sera, 98.9% and 93.8% with sheep sera, and 70.8% and 79.8% with dog sera. The IELISA using B. canis RLPS antigen resulted in sensitivity and specificity values of 97.0% and 97.4%, respectively, with bovine sera, 96.2% and 96.3% with sheep sera, and 95.8% and 98.8% with dog sera. Labeling RLPS core from B. ovis and B. canis with fluorescein was not successful. B. abortus RB51 core labeled with fluorescein resulted in sensitivity and specificity values of 93.5% and 99.8%, respectively, with bovine sera and 78.1% and 99.0% with sheep sera. It was not possible to test the dog sera in the FPA.

Animals↗
PubMed2001

Fluorescence polarization assay for the diagnosis of bovine brucellosis: adaptation to field use.

A fluorescence polarization assay (FPA) was used to test whole blood samples prepared by mixing blood cells from cattle without exposure to Brucella abortus (B. abortus) with sera from animals with confirmed (bacteriologically) infection. A cut-off value between negative and positive values was initially established to be 87.2mP. This value was changed to 95mP to increase assay specificity without loss of sensitivity when testing blood samples from negative animals. The FPA technology was applied to whole blood samples in the field and to stored whole blood samples using two diluent buffers. Relative sensitivity and specificity values for the FPA performed in the field, based on buffered antigen plate agglutination test and competitive enzyme immunoassay results were 95.3 and 97.3%, respectively. However, to obtain maximum sensitivity and specificity, a cut-off value of 105mP was determined for fresh whole blood samples. The relative sensitivity and specificity values of the FPA when testing stored whole blood samples were 100% each using a 95mP cut-off.The usefulness of the FPA for testing whole blood samples in the field was demonstrated.

Agglutination Tests↗
PubMed2001

Validation of the fluorescence polarization assay for detection of milk antibody to Brucella abortus.

A fluorescence polarization assay (FPA) for detection of antibody to Brucella abortus in individual milk samples was developed and validated. Samples from 190 cattle from which B. abortus was isolated; milk samples from cattle in herds infected with B. abortus (n = 1,086) and positive in the milk ring test (MRT), as well as milk samples from Canadian cattle (with no evidence of brucellosis, n = 2,974) were tested by the indirect enzyme immunoassay (IELISA) and the FPA. The sensitivity (based on samples from culture positive cattle) and specificity (based on Canadian milk samples) of the IELISA and the FPA were 100%. The relative sensitivity value obtained with milk from cattle of infected herds and the specificity values of the IELISA were 98.5 and 99.9%, respectively. The relative sensitivity and specificity of the FPA with the same samples were 82.2 and 99.4% using a cutoff value of 90 millipolarization units (mP). The low relative sensitivity value of the FPA was shown, by competitive enzyme immunoassay (CELISA), to be due to vaccinal antibody (assumed as vaccinal antibody against B. abortus Sl19 is excluded by the FPA and CELISA but not by the MRT and the IELISA), present in some of the milk samples. The FPA is a homogeneous assay which, unlike the MRT and the IELISA, may be used for testing in the field.

Animals↗
PubMed1988

Spatial organization of the retinal projection to the avian lentiform nucleus of the mesencephalon.

Utilizing the horseradish peroxidase retrograde tracing technique and the 2-deoxy-D-glucose metabolic mapping technique, we have demonstrated in chickens the distribution of retinal ganglion cells that project to the lentiform nucleus of the mesencephalon (LM) and the retinotopic organization of the projection in the LM. Retinal ganglion cells labeled after a nearly complete injection into the LM were found in the four quadrants, distributed in a wide horizontal belt lying along both sides of the retinal equator and stretching from the temporal to the nasal retina. The HRP-labeled cells, which appeared round or oval, ranged from 25 to 840 micron 2 in size with most in the smaller size range. Results of partial HRP injections into the LM and metabolic mapping patterns in the LM produced by stimulation of half the retina with horizontal visual motion suggest that there is an orderly mapping of the retina onto the LM. The inferior temporal quadrant projects to the rostrodorsal LM; the inferior nasal quadrant projects to the caudodorsal LM. The superior temporal quadrant projects to the middle and ventral LM, extending from the rostral to the caudal pole, whereas the superior nasal quadrant projects to a small zone in the caudal LM. The mapping of the retinal quadrants in the LM is remarkably similar to that reported in the optic tectum of birds. We suggest that a common embryological anlage with the optic tectum and the arrangement of retinal axons in the optic tract are important factors in establishing the retinotopic organization of the LM.

Animals↗
PubMedDate not supplied

The retinal targets of centrifugal neurons and the retinal neurons projecting to the accessory optic system.

In birds, neurons of the isthmo-optic nucleus (ION), as well as "ectopic" neurons, send axons to the retina, where they synapse on cells in the inner nuclear layer (INL). Previous work has shown that centrifugal axons can be divided into two anatomically distinct types depending on their model of termination: either "convergent" or "divergent" (Ramon y Cajal, 1889; Maturana & Frenk, 1965). We show that cytochrome-oxidase histochemistry specifically labels "convergent" centrifugal axons and target neurons which appear to be amacrine cells, as well as three "types" of ganglion cells: two types found in the INL (displaced ganglion cells) and one in the ganglion cell layer. Labeled target amacrine cells have distinct darkly labeled "nests" of boutons enveloping the somas, are associated with labeled centrifugal fibers, and are confined to central retina. Lesions of the isthmo-optic tract abolish the cytochrome-oxidase labeling in the centrifugal axons and in the target amacrine cells but not in the ganglion cells. Cytochrome-oxidase-labeled ganglion cells in the INL are large; one type is oval and similar to the classical displaced ganglion cells of Dogiel, which have been reported to receive centrifugal input; the other type is rounder. Rhodamine beads injected into the accessory optic system results in retrograde label in both types of cells, showing that two distinct types of displaced ganglion cells project to the accessory optic system in chickens. The ganglion cells in the ganglion cell layer that label for cytochrome oxidase also project to the accessory optic system. These have proximal dendrites that ramify in the outer inner plexiform layer.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗